Application of flowcytometrically sexed spermatozoa in different farm animal species: a review
The most efficient way to shift the sex ratio of offspring is to select spermatozoa according to the sex chromosomes. The difference of their DNA-content can be used by flowcytometry to produce populations of either sex at high accuracy. As the method is based on single cell identification, the output of cells is limited, although major improvements were made by high-speed flowcytometry and improved cell orientation in front of the UV-Laser. The state of art is described in this review for the main farm animal species. For bovine AI sex-sorted-frozen spermatozoa are already available on commercial basis, whereas in other species, especially in pigs, the high demand of spermatozoa can hardly be satisfied. However, in combination with other biotechniques like IVF, ICSI, GIFT and special insemination protocols litters of acceptable size were produced under laboratory condition. As in horses and sheep current research is focused in pigs on long time storage of the sex sorted spermatozoa in liquid nitrogen.